The two people, who were visiting from North Carolina, took immediate action, according to officials.

"[The man] jumped into the pool right away, began CPR," said BSO spokeswoman Keyla Concepcion. "That's when the female, his companion, noticed the second body in the pool and also pulled that girl out."

The girls, identified as Harmani and Harmony West, were airlifted to Broward Health Medical Center, but could not be revived.

Authorities said the lock to the pool where the toddlers were found was broken, and other bodies of water around the complex are not gated.

"There's a lake right behind the family's apartment building," Concepcion said. "There were a number of bodies of water where children could have drowned."

Witness Ester Campos said neighbors think the mother was sleeping when the incident took place.

"If there's any message at all it's that children must be supervised," said Broward Fire Rescue Spokesman Mike Jachles. "Children should know how to swim. Parents and children who are old enough should learn CPR."